The effect of spinal anesthesia on pain perception and
sedation in healthy volunteers

- ACRONYM

SAPP

- hypothesis

Spinal anesthesia induces several alterations in normal brain processes. Firstly, loss of afferent information increases pain
sensitivity. In our previous study on the effects of spinal anesthesia (P11.221) we showed that subjects felt more pain upon heat
stimulation during spinal anesthesia. This increase in pain sensitivity was explained by alterations in the endogenous pain
modulation system, which is an important regulator of pain perception. Secondly, clinical evidence suggests that the loss of
afferent information from the spinal cord has significant effects on the maintenance of the arousal state. For example, spinal
anesthesia coincides with the development of a decrease in the necessary dose of intravenous or inhalational anesthesia to
reach a defined level of sedation. Furthermore, an increased level of sedation has been shown in healthy volunteers with spinal anesthesia. The aim of the current study is to extend and specify the results seen in our previous study within specific pain processing brain areas with task-related fMRI data, and to evaluate experimental pain sensitivity and sedation after spinal anesthesia.

Spinal anesthesia induces several alterations in normal brain processes. Firstly, loss of afferent information increases pain sensitivity. Secondly, clinical evidence suggests that the loss of afferent information from the spinal cord has significant effects on the maintenance of the arousal state.

In this study the effects of deafferentation on pain perception and sedation will be further investigated by 1) performing task-related functional MRI and 2) performing behavioral pain tests to evaluate endogenous pain modulation.

Task-related fMRI: To determine the specific effects of deafferentation, two task-related fMRI scans will be performed to (1) detect the specific process of altered pain perception in the brain; and (2) measure reaction time as marker for sedation and identify alterations in brain regions involved in this process.

Endogenous pain modulation: A disbalance between pain facilitation and pain inhibition alters pain sensitivity and plays an important role in the chronification of pain. To evaluate the effect of deafferentation on the endogenous pain modulation system two experimental expressions of this system will be investigated known as the “Conditioned pain modulation” and “Offset analgesia” paradigm [10].

Aims:
(1) To assess the effect of deafferentation on pain processing in the brain by task-fMRI
(2) To assess the effect of deafferentation on reaction time (sedation) by task-fMRI
(3) To assess the effect of deafferentation on endogenous pain modulation